The present invention relates to a lifting mechanism. More particularly, the invention relates to an adaptor or attachment used in combination with a cable or chain to lift relatively heavy plates used to cover trenches containing electrical power and/or data lines.
In recent years, many utilities have employed ground trenches for running electrical power and data lines. These trenches may be fabricated from steel, concrete, or composite materials and are intended to contain and protect the electrical lines, while affording ready access to them. Typically, each trench is covered by a series of plates which are placed end to end over the length of the trench and rest in recess running along the top edges of the trench sidewalls. Like the trenches, the cover plates may be fabricated from steel, concrete, or various composites and each may weigh as much as 50 to 100 pounds. The weight of the cover plates, alone, makes it difficult to place, remove and replace the plates when installing the trenches or servicing the electrical lines contained in them. In addition, sand or gravel may become lodged in the small spaces separating the individual plate segments or between the plate segments and trench walls, making removal of the covers even more difficult. When the covers are lodged or wedged in place due to a tight spacing between adjacent cover(s) and/or the lodging of sand or gravel, for example, the initial lifting force required to dislodge even a 50–100 pound cover may be as much as hundreds of pounds. In such an instance, the use of manual tools, such as crowbars or hand held lift hooks, has obvious limitations.
The present invention is directed to the problem of removing these ground trench cover plates.